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I e-mailed Billy Godbolt last week to see if I could get a little more V-Rod specific turbo cam information. He pretty much told me the same thing he said in the article. If it is a good modern turbo, and it is matched up to the engine properly, the manifold pressure and the back pressure should be close to equal. If this is the case, overlap is not going to be an issue. He said once you start getting higher back pressure than intake pressure, the engine will become real overlap sensitive. He said he thinks the SE-2's would work good in a turbocharged race engine, but if you are worried run smaller cams. Keep in mind I'm still trying to learn more about what works best in a turbocharged engine cam wise and this is just one cam designer's opinion.
 

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So with the Trask GT 25 Where are we with boost pressure vs back pressure ? Isn't that calculated by the trim settings ? What about a street motor where we need more grunt at lower rpms? Any insight appreciated !
 

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So with the Trask GT 25 Where are we with boost pressure vs back pressure ? Isn't that calculated by the trim settings ? What about a street motor where we need more grunt at lower rpms? Any insight appreciated !
I think you would have to measure back pressure before the turbo and boost pressure to see what kind of pressures you have at all rpm's.
 

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I will have some results to report in about a month. I'm still fabricating headers. I used a GT2554 turbo with a .80 A/R ratio. The comperessor map looks just right for what I want. I used the stock intake cam on the exhaust and an SE cam for the intake. The lobe centers are 112 Intake and 114 Exhaust. I settled on those numbers after a lot of reading and talking to others. I have ported and polished heads and I used 1 3/4" pipe for the headers. I will tune it with a Twin Scan 88 data logger with A/F probe and dual EGT sensors.
 

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Killer Service Inc.
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Dale sorry about the post I ment a 1130 intake cams.
 

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Silversurfer, curious as to your choice of 1 3/4 header pipe. ' Prevailing' logic has it that the smallest 'reasonable' size head pipe (1 1/2) would yield higher velocity and therefore quicker turbo spool-up. Several discussions on this topic on ls1tech.com. Also discussed in the book 'Maximum Boost' by Corky Bell.

Not doubting your choice, just looking for knowledge/information. Has anyone considered a 'reversion step' in their header design? I really like where this discussion is going!

What EGT sensor setup are you using? Please keep us updated on your results.. Sound like a great project.!
 

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Has anyone considered a 'reversion step' in their header design? I really like where this discussion is going!

What EGT sensor setup are you using? Please keep us updated on your results.. Sound like a great project.!
I used 1 3/4" headers for the reasons you mentioned. They are a step down from the stock header and the exhaust port is 1 3/4".
Last year I didn't know so much and used the stock header diameter. Even if it's only 1/8" smaller the difference looks huge. Last year I also tried to use O2 sensors in the headers and since then learned they do not like the pressure build up in the headers. This year I will have a wide band O2 sensor after the turbo and use EGT probes in the headers to check balance. I am using the Koso dual EGT meter. It has a neat display that turns red if you reach an adjustable preset temperature.
As far as exhaust recursion, it may have worked itself out. The flange adapter I had machined for the header is a copy of the stock header on the outside and tapers to the 1 3/4" pipe on the inside. The exhaust leaving the port is is guided like a funnel into the pipe. But there is a gap where the gasket sits. So a reverse flow hits the expanding taper and the lip of the exhaust port where the gasket seats.
 

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Silversurfer, curious as to your choice of 1 3/4 header pipe. ' Prevailing' logic has it that the smallest 'reasonable' size head pipe (1 1/2) would yield higher velocity and therefore quicker turbo spool-up. Several discussions on this topic on ls1tech.com. Also discussed in the book 'Maximum Boost' by Corky Bell.

Not doubting your choice, just looking for knowledge/information. Has anyone considered a 'reversion step' in their header design? I really like where this discussion is going!

What EGT sensor setup are you using? Please keep us updated on your results.. Sound like a great project.!
one of the best methods to minimize reversion is an intake valve with a wider margin around the vavle allowing a small 45 degree cut on the chamber side of the valve...this really reduces reversion flow into the intake port...
 

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Thanks for the info. Considering this cam combo myself. Looking forward to your results/impressions.

LBrown; confused by your statement. Understand a wider margin, but the valve seat angle is already 45 degrees. Are you suggesting back cutting the valve?
Stock cylinder head seat angles are chamber side 30, seat 46, port side 70 degrees.
Just not getting a clear picture of what you are suggesting.
 

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Autobanmod
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Discussion Starter · #52 ·
The spec sheets I have from Jones cams and Compcams show the exhaust cams to be 235° @ 1mm lift. My 2006 VRSCR manual shows 206° @ 1mm lift. I still have my stock exhaust cams and will be happy to measure them some time this week.
Messrs Schrick finished measuring the cams and they also come up with 235° @ 1mm lift for the exhaust.
The stamping on the intake reads 17419-01k, the exhaust 17421-01k

I will soon receive the results and will keep you updated.
So sad that Tim is gone...feels weird to keep on posting inside this thread as if nothing has happened, his input will be dearly missed.
 

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Autobanmod
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Discussion Starter · #53 ·
here we go,
#1 is the diagram for the stock cams
#2 shows combinations for stock cams, i.e. if you swap intake and exhaust cams
#3 would show proposed alternatives by remachining, but that will remain my little secret ;)
 

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So sad that Tim is gone...feels weird to keep on posting inside this thread as if nothing has happened, his input will be dearly missed
It is sad, but I think he would be happy that we are moving ahead.
 

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Jan explain the charts for those that are looking and do not understand.

Chart one what cams are what intake exhaust is it a 1130 or 1250...ect

Secrets are not allowed.

so then also how would these cams work with a SC ?

Thanks
Rod
 

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Autobanmod
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Discussion Starter · #56 ·
Jan explain the charts for those that are looking and do not understand.

Chart one what cams are what intake exhaust is it a 1130 or 1250...ect

Secrets are not allowed.

so then also how would these cams work with a SC ?

Thanks
Rod
The charts show the cam lift over degree crankshaft for a 2003 VRSCA model with 1130cc. This is what I have installed now.
0° is top dead center (TDC) of the piston
The red chart is for the exhaust cam, the black chart is for the intake cam.
The numbers under each chart show the opening/closing values in °crank for the individual cams @ 1mm lift and @ TDC.
EÖ stands for intake opens
ES stands for intake closes
AÖ stands for exhaust opens
AS stands for exhaust closes
The charts just show stock cams, nothing else.

It would cost me 2000 $ to have four cams redesigned/machined and I'm not posting the conclusion here just to have them copied by some smartass who wants to jump the train to make some easy bucks... This is not rocket science, any cam maker can do it.
Just these charts above have already cost me about 200$.
 

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Killer Service Inc.
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It would cost me 2000 $ to have four cams redesigned/machined and I'm not posting the conclusion here just to have them copied by some smartass who wants to jump the train to make some easy bucks... This is not rocket science, any cam maker can do it.
Just these charts above have already cost me about 200$.

:them::them:

We do not need this and we know they are watching.

We...the turbo clan should come together and get a fund set up to do this.

This way we will know that it is done the right way.

Just a thought.

Thanks you sharing your thoughts

rod
 

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Autobanmod
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Discussion Starter · #58 ·
In principle the conclusion is confirming exactly what Tim wrote to me by PM. :notworth:
He asked me not to post this in public and told me that he plans to publish his findings once his LSR project is done.
So I suggest we let this rest a little bit and see what happens.
 

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It wold be great if Doherty would come up with a set of turbo cams based on their research on the 'Great White Dyno.' As for now, I'm interested in Silversurfers results. If good its a great budget option for us 'ordinary' folks. Already got the cams just need the time to do the swap and see for myself. Thanks for sharing your ideas/experiments!
 

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Thanks for the info. Considering this cam combo myself. Looking forward to your results/impressions.

LBrown; confused by your statement. Understand a wider margin, but the valve seat angle is already 45 degrees. Are you suggesting back cutting the valve?
Stock cylinder head seat angles are chamber side 30, seat 46, port side 70 degrees.
Just not getting a clear picture of what you are suggesting.
no sorry i didn`t make it more clear... if you put a 45 degree cut on the chamber side of the intake valve the flow in the reverse direction is cut way down reducing reversion... hd actually recomends on big twins cutting the chamber side of the valves with a 45 degree cut if you have a problem with valve to valve clearance... that works well on the intake as it cuts down reversion but it absolutely kills the flow out the exhaust valve...wegner automotive that does all the cnc work for hd do the chamber side cut on the intake valve on engines that need a wide power band..the best flowing exhaust valves have some tulip shape and the wider the margin the better it will flow(usually)... at the top of the margin a small radius ..
 
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